JP5182021B2 - Digital camera - Google Patents

Description

  The present invention relates to a digital camera that images a subject and generates image data.

It is desired that a digital camera has a large number of images that can be shot with one charge. Therefore, in order to increase the battery duration and increase the number of shots, a system has been proposed in which a solar cell (for example, Patent Document 1) configured on a silicon substrate is provided in an image sensor and the battery is charged with power generated by the solar cell. ing.
JP 2008-66402 A

  However, a solar cell such as an a-Si (amorphous silicon) solar cell has a problem in that the device becomes large, for example, it impairs the design of the digital camera or requires the addition of parts. In addition, when power generation is performed by an image sensor provided with such a solar cell, the pixel area of the image sensor is reduced, which may cause a decrease in sensitivity.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a digital camera capable of extending the battery duration without impairing the design of the digital camera.

In order to solve the above problems, a typical configuration of a digital camera according to the present invention includes an imaging lens, an imaging device that captures an image of a subject and generates image data, and transmits visible light to the imaging device. A photoelectric conversion unit that functions as an optical filter and converts ultraviolet light into electric power, and a charging circuit that charges the battery with the electric power converted by the photoelectric conversion unit. The photoelectric conversion unit includes an imaging lens and an imaging element. It is characterized by being located between .

  The digital camera further includes a power amount detection unit that detects the amount of power charged in the battery, a light source estimation unit that estimates the illumination light source of the subject according to the detected power amount, and the estimated illumination light source And a calculating unit that calculates a white balance correction value of the image data.

  The digital camera is further estimated by a power amount detection unit that detects the amount of power converted by the photoelectric conversion unit, and a light source estimation unit that estimates the illumination light source of the subject according to the detected power amount. A calculation unit that calculates a white balance correction value of the image data in accordance with the illumination light source.

  The light source estimation unit estimates that the illumination light source is the sun when the amount of power is equal to or greater than the first threshold, and estimates that the illumination light source is the illumination device when the amount of power is smaller than the first threshold. You can do it.

  The digital camera further includes a first mode when the illumination light source is estimated to be the sun based on an estimation result of the light source estimation unit, and a first mode when the illumination light source is estimated to be the illumination device. The mode switching unit for switching between the two modes may be provided, and the calculation unit may calculate the white balance correction value according to the mode switched by the mode switching unit.

  The first mode includes a clear sky mode and a cloudy sky mode, and the mode switching unit switches to the clear sky mode when the detected electric energy threshold is larger than the second threshold, and is smaller than the second threshold. In this case, switch to cloudy mode.

  The charging circuit may switch ON / OFF the charging of the battery according to the remaining charge of the battery.

  ADVANTAGE OF THE INVENTION According to this invention, the digital camera which can lengthen battery duration can be provided, without impairing the design of a digital camera.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do. Further, signals and currents are expressed by the codes of the lines through which they pass.

(Transparent solar cell)
FIG. 1 is a block diagram of a digital camera showing an embodiment of the present invention. The digital camera 100 functions as an image sensor 102 that captures an image of a subject and generates image data, and an optical filter that transmits visible light and causes the image sensor 102 to receive light, and as a photoelectric conversion unit that converts ultraviolet light into electric power. The transparent solar cell 104 and a charging circuit 108 for charging the battery 106 with the electric power converted by the transparent solar cell 104 are provided.

  An imaging device such as a CCD (Charge Coupled Device) has light receiving sensitivity to ultraviolet rays and infrared rays. On the other hand, the human eye has sensitivity in a wavelength band of about 400 nm to 700 nm. Natural light such as sunlight contains ultraviolet light and infrared light components, and when the image sensor receives the light, the color reproducibility is affected. For this reason, in a digital camera, an optical filter for cutting an ultraviolet ray / infrared ray component is usually provided in front of an image sensor.

  In this embodiment, a transparent solar cell 104 that also functions as an optical filter is provided in place of the optical filter at a position where such an optical filter is normally provided. As the transparent solar cell 104, for example, a photovoltaic cell described in Patent Document 2 that converts ultraviolet rays into electric power may be used. As described in this document, a transparent solar cell can be manufactured by forming a film such as a zinc oxide semiconductor (n-type) or a copper aluminum oxide semiconductor (p-type) on a glass substrate.

  FIG. 2 is a schematic diagram showing an example of spectral transmittance characteristics of a transparent solar cell, and FIG. 3 is a graph showing an example of such spectral transmittance characteristics. As can be seen from FIGS. 2 and 3, the transparent solar cell 104 transmits visible light 115, absorbs ultraviolet light 116 and photoelectrically converts it, and reflects infrared light 117. This is a spectral transmittance characteristic similar to that of an optical filter in which thin films having different refractive indexes are stacked on a glass substrate to transmit a specific wavelength.

  Therefore, the transparent solar cell 104 can function as an optical filter. The light rays that the transparent solar cell 104 photoelectrically converts (generates power) are exclusively ultraviolet rays 116 included in sunlight (natural light).

  According to said structure, since the electric power which the transparent solar cell 104 generated is charged to the battery 106, it is possible to lengthen battery duration. In addition, since the transparent solar cell 104 is positioned between the image pickup lens 210 and the image pickup element 102, which is usually provided with an optical filter, the pixel area is reduced unlike the technique of generating power by the image pickup element 102 itself. There is no end to it.

(Remaining amount detection unit)
As shown in FIG. 1, the digital camera 100 further includes a power amount detection unit (remaining amount detection unit 110) that detects the amount of power charged in the battery 106, and illumination of the subject according to the detected power amount. A light source estimation unit 112 that estimates a light source and a calculation unit 114 that calculates a white balance correction value of image data according to the estimated illumination light source.

  As described above, the transparent solar cell 104 exclusively generates electric power by photoelectrically converting the ultraviolet rays 116 and charges the battery 106. Therefore, if the amount of electric power (charge amount) charged in the battery 106 is detected, it can be estimated with high accuracy whether or not the illumination light source contains a lot of ultraviolet rays 116.

  In the present embodiment, as described above, the remaining amount detection unit 110 detects the amount of power (charge amount) charged in the battery 106. However, instead of the remaining amount detection unit 110, a power generation amount detection unit 111 that is virtually indicated by a broken line is provided to detect the power amount converted by the transparent solar cell 104, that is, the power generation amount before charging the battery 106. The amount of power may be detected at the position.

  Even in the above-described configuration, it is possible to estimate with high accuracy whether or not the illumination light source contains a large amount of ultraviolet light by using the property of the transparent solar cell 104 that exclusively generates photoelectric light by converting the ultraviolet light 116.

(Light source estimation unit)
The light source estimation unit 112 estimates that the illumination light source is the sun when the amount of power is equal to or greater than the first threshold value, and that the illumination light source is an illumination device when the power amount is smaller than the first threshold value. presume. In the present embodiment, when it is exactly equal to the first threshold value, it is estimated to be the sun, but may be estimated to be a lighting device.

  Comparing sunlight and lighting equipment, sunlight is overwhelmingly the most ultraviolet light. Here, it is estimated that a light source with a large amount of ultraviolet light is sunlight, and a light source with a small amount of ultraviolet light that is not so is estimated to be lighting equipment.

(Mode switching part)
FIG. 4 is a diagram showing various modes for white balance adjustment recorded in the ROM 350 of the digital camera. The digital camera 100 further includes a first mode when the illumination light source is estimated to be the sun based on the estimation result of the light source estimation unit 112, and a first mode when the illumination light source is estimated to be the illumination device. The mode switching unit 122 that switches between the two modes is provided, and the calculation unit 114 calculates the white balance correction value according to the mode switched by the mode switching unit 122.

  According to this embodiment, based on the estimation result of the light source estimation unit 112, it is possible to switch to the first mode assuming that the light source is the sun or the second mode assuming that the light source is a lighting device. . Thereby, a more appropriate white balance correction value can be calculated.

(Sunny mode and cloudy mode)
The first mode includes a clear sky mode and a cloudy sky mode, and the mode switching unit 122 switches to the clear sky mode when the detected threshold value of electric energy is larger than the second threshold value. If it is smaller, switch to cloudy mode. In addition, when it is exactly equal to the second threshold value, it may be switched to either the clear sky mode or the cloudy mode.

  According to said structure, a more suitable white balance correction value is computable by making the 1st mode when the light source determines with the sun into the subdivided mode. The white balance correction value is obtained by dividing the output of the image sensor 102 into, for example, an area of 16 pixels × 16 pixels, and the sensitivity ratio R / G and R (red), G (green), and B (blue) output from each area. B / G is calculated and determined based on the statistics of the sensitivity ratio.

(Charging ON / OFF)
The charging circuit 108 switches on / off the charging of the battery 106 according to the remaining charge of the battery 106. This ON / OFF switching is performed when the CPU 250 switches the switch 124.

  When the battery 106 is saturated or the battery 106 is charged with a certain amount of power, it is not necessary to charge the battery 106 any more. However, it is desirable to continue the photoelectric conversion in order to improve the accuracy of calculating the white balance correction value. Therefore, the switch 124 is opened and only charging is turned off, and the electric power converted by photoelectric conversion is not charged to the battery 106 but discarded. That's fine.

(Digital camera configuration)
5A and 5B are diagrams showing an example of the appearance of the digital camera. FIG. 5A is a diagram seen from the front, and FIG. 5B is a diagram seen from the back. Other configurations of the digital camera will be described below with reference to FIGS. 5 and 1. The imaging element 102 may be a CCD (Charge Coupled Device) and is an imaging unit that images an object scene and generates an electronic image signal, and has, for example, 1600 × 1200 pixels. The imaging element 102 converts the light image of the subject formed by the imaging lens 210 into image signals of R (red), G (green), and B (blue) color components for each pixel (pixels received by each pixel). A signal comprising a signal sequence of signals) and output.

  An image signal (analog signal) obtained from the image sensor 102 is given to the analog signal processing circuit 230. The analog signal processing circuit 230 is a circuit that performs predetermined analog signal processing on the image signal. The analog signal processing circuit 230 includes at least a correlated double sampling circuit (Correlated Double Sampling: CDS, not shown) and an auto gain control (Auto Gain Controlled: AGC, not shown) circuit. Noise reduction processing of the image signal is performed by the correlated double sampling circuit, and the level of the image signal is adjusted by adjusting the gain by the auto gain control circuit.

  The A / D converter 240 converts each pixel signal of the image signal into, for example, a 12-bit digital signal. The converted digital signal is supplied to a central processing unit (CPU) 250 and temporarily stored in a RAM (Random Access Memory) 260 as image data. The image data stored in the RAM 260 is subjected to color correction processing or the like by the image processing unit 280 and then subjected to compression processing or the like by the compression / decompression unit 290.

  An audio signal such as an environmental sound obtained from the directional microphone 300 is input to the audio processing unit 310. The audio signal input to the audio processing unit 310 is converted into a digital signal by an A / D converter (not shown) provided in the audio processing unit 310 and temporarily stored in the RAM 260. The digitized audio signal is sent again to the audio processing unit 310 and can be reproduced from the speaker 320.

  The operation unit 330 includes a power button 330 </ b> A, various operation buttons 330 </ b> B, a shutter release button 330 </ b> C, and the like, and is used when the user changes the setting of the digital camera 100 or performs an imaging operation.

  The CPU 250 comprehensively controls the above-described units by executing predetermined programs recorded in a RAM 260 and a ROM (Read Only Memory) 350. The RAM 260 is a high-speed accessible semiconductor memory, and the ROM 350 is configured as a non-volatile semiconductor memory (for example, a flash ROM) that cannot be electrically rewritten. A part of the area in the RAM 260 functions as a temporary storage buffer area, and temporarily stores image data and audio data.

  Each processing unit 280, 290, 310 of the CPU 250 is a functional part realized by the microcomputer executing a predetermined program.

  The image processing unit 280 is a processing unit that performs various digital image processing such as WB (white balance) processing and γ correction processing. The WB process is a process for adjusting the color balance by converting the level of each of the R, G, and B color components based on the white balance correction value calculated by the calculation unit 114. The γ correction process is a process for converting the pixel data level. This is a process for correcting the key. The compression / decompression unit 290 further compresses the image data that has been subjected to color correction processing and the like by the image processing unit 280. As the compression method, for example, a JPEG (Joint Photographic Experts Group) method or the like is adopted. The audio processing unit 310 is a processing unit that performs various digital processes on audio data.

  The CPU 250 having such a configuration performs processing in an imaging mode and a reproduction mode. For example, in the imaging mode, the imaging device 102 is first set to a viewfinder (LCD 380) image output operation mode, imaging is performed at a predetermined cycle (for example, 30 frames / second), and image data corresponding to the imaging is sequentially obtained. Output (preliminary imaging). Image data output from the image sensor 102 is displayed as a viewfinder image on the LCD 380 via the analog signal processing circuit 230, the A / D converter 240, and the image processing unit 280. In this state, when the shutter release button 330C is half-pressed (S1 state) by the user, the CPU 250 determines the AE (Auto Exposure) evaluation value and AF (Auto (Auto Exposure) evaluation value) based on the preliminary image data input from the image sensor 102. Focus) Find the evaluation value. The CPU 250 obtains the in-focus position based on the AF evaluation value by a known hill-climbing method, for example, and moves the imaging lens 210 to the in-focus position using the AE / AF unit 360. Further, the CPU 250 determines the shutter speed (charge accumulation time in the image sensor 102) at the time of actual imaging, the aperture value of the imaging lens 210, and the gain value of auto gain control in the analog signal processing circuit 230 based on the AE evaluation value.

  When the shutter release button 330C is fully pressed (main imaging, S2 state) in the imaging mode, the CPU 250 sets the operation mode of the image sensor 102 to the operation mode for main imaging, and images the subject. The compression / decompression unit 290 generates a compressed image based on the captured image data acquired in step (1). The compressed high resolution image data is recorded on the recording medium 370. For example, an SD card (registered trademark) can be used as the recording medium 370.

  Further, the CPU 250 can fetch a program that operates on the digital camera 100 from the recording medium 370. For example, the control program recorded on the recording medium 370 can be taken into the RAM 260 or the ROM 350. Thereby, the control program can be updated.

  An LCD (Liquid Crystal Display) 380 is a display device that displays an object scene, displays various menus for the user, and provides information for operation. The flash 390 is a light-emitting device that emits photographing auxiliary light and irradiates a subject while light emission is permitted.

  According to the present embodiment, since the power generated by the photoelectric conversion unit is charged in the battery, the battery duration can be increased. In addition, since the photoelectric conversion unit functions as an optical filter and is positioned between the imaging lens and the imaging device, the pixel area is not reduced unlike the case where power generation is performed by the imaging device itself.

  According to the present embodiment, the photoelectric conversion unit exclusively generates electric power by photoelectrically converting ultraviolet rays and charges the battery. Therefore, if the amount of electric power (charge amount) charged in the battery is detected, it can be estimated with high accuracy whether or not the illumination light source contains a lot of ultraviolet rays.

  According to the present embodiment, it is possible to estimate with high accuracy whether or not the illumination light source includes a large amount of ultraviolet light, by utilizing the property of a photoelectric conversion unit that generates electricity by photoelectrically converting ultraviolet light.

  According to the present embodiment, based on the estimation result of the light source estimation unit, it is possible to switch to the first mode assuming that the light source is sunlight or the second mode assuming that it is a lighting device. . Thereby, a more appropriate white balance correction value can be calculated.

  According to the present embodiment, a more appropriate white balance correction value can be calculated by changing the first mode when the light source is determined to be sunlight to a more subdivided mode.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention can be used in a digital camera that captures an image of a subject and generates image data.

It is a block diagram of a digital camera showing an embodiment of the present invention. It is a schematic diagram which shows the spectral transmittance characteristic of a transparent solar cell. It is a graph which shows the spectral transmittance characteristic of a transparent solar cell. It is a figure which shows the various modes for white balance adjustment recorded on ROM of a digital camera. It is a figure which shows an example of the external appearance of a digital camera.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Digital camera, 102 ... Image pick-up element, 104 ... Transparent solar cell, 106 ... Battery, 108 ... Charging circuit, 110 ... Electric energy detection part, 112 ... Light source estimation part, 114 ... Calculation part, 116 ... Ultraviolet ray, 122 ... Mode switching unit, 124 ... switch, 210 ... imaging lens, 230 ... analog signal processing circuit, 240 ... A / D converter, 250 ... CPU, 260 ... RAM, 280 ... image processing unit, 290 ... compression / decompression unit, 300 ... Directional microphone 310 ... Audio processing unit 320 ... Speaker 330 ... Operation unit 330A ... Power button 330B ... Operation button 330C ... Shutter release button 350 ... ROM 360 360 AE / AF unit 370 ... Recording medium 380 LCD, 390 Flash

Claims (7)

An imaging lens;
An image sensor that images a subject and generates image data;
A photoelectric conversion unit that functions as an optical filter that transmits visible light and causes the image sensor to receive light, and converts ultraviolet light into electric power;
A charging circuit for charging the battery with the electric power converted by the photoelectric conversion unit;
Equipped with a,
The digital camera , wherein the photoelectric conversion unit is located between the imaging lens and the imaging device . The digital camera of claim 1, further comprising:
An electric energy detector for detecting the electric energy charged in the battery;
A light source estimation unit that estimates an illumination light source of the subject according to the detected amount of power;
A calculation unit that calculates a white balance correction value of the image data in accordance with the estimated illumination light source;
A digital camera comprising: The digital camera of claim 1, further comprising:
An electric energy detector that detects electric energy converted by the photoelectric converter;
A light source estimation unit that estimates an illumination light source of the subject according to the detected amount of power;
A calculation unit that calculates a white balance correction value of the image data in accordance with the estimated illumination light source;
A digital camera comprising: The digital camera according to claim 2 or 3,
The light source estimation unit estimates that the illumination light source is the sun when the amount of power is equal to or greater than a first threshold, and if the amount of power is smaller than the first threshold, the illumination light source is a lighting device. A digital camera characterized by presuming that there is. 5. The digital camera according to claim 4, further comprising:
Based on the estimation result of the light source estimation unit, a first mode when the illumination light source is estimated to be the sun, and a second mode when the illumination light source is estimated to be an illumination device. A mode switching part for switching
The digital camera according to claim 1, wherein the calculation unit calculates the white balance correction value according to a mode switched by the mode switching unit. 6. The digital camera according to claim 5, further comprising:
The first mode includes a clear sky mode and a cloudy mode,
The mode switching unit switches to a clear sky mode when the detected threshold value of electric energy is larger than a second threshold value, and switches to a cloudy mode when smaller than the second threshold value. . The digital camera according to any one of claims 1 to 6,
The digital camera according to claim 1, wherein the charging circuit switches ON / OFF charging of the battery according to a remaining charge amount of the battery.